[SI-LIST] Re: 0.8mm BGA routing
- From: Dimiter Popoff <dimiter.popoff@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Fri, 26 Dec 2003 20:49:18 +0200
I was asked off-line how I achieved the miracles described in
my former message. While the numbers clearly don't add up,
I am posting my reply to make sure I won't mislead anyone.
> How did you fit three 5 mil traces between pads ...
I did not.
I was thinking of the 1.27mm pitch BGAs I routed 3-4 years ago,
since then I've been mostly programming.
Oddly, I did check whether the guy was not asking about 0.8mm (I have
my nightmares regarding 0.8mm BGAs since that time and probably soon
enough they'll come true), but somehow picked the wrong bit state.
I guess I've been somewhere else...
Dimiter
--------------------------------------------------------------------
Dimiter Popoff
Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria
http://transgalactic.freeyellow.com
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Dimiter Popoff
> Sent: Wednesday, December 24, 2003 10:34 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: 0.8mm BGA routing
>
>
> Tayyab Jamil Qureshi,
>
> I have been successfull with these using 5 mil resolution.
> This allowed 3 traces between the BGA pads; also, I put a
> via on all BGA pads, hole was drilled 0.3mm thus getting
> about 0.2mm after plating. This leaves 0.508mm (20 mil)
> pad diameter - and allowed me to route the whole mess
> without sacrificing any area on two signal layers (and 4
> planes).
> There is an important detail with the through-holes on
> every BGA pad. Sometimes some of the solder balls on the
> BGA package are not well attached; this may result into
> losing the ball during reflow (it just flows through the hole
> to form a bubble on the bottom of the board).
> My solution to that was to reflow all BGA packages with
> some flux once belly up; this makes sure all balls are
> really soldered to the package, and surface tension does
> the rest of the job during the final reflow (it does it for
> most of the balls either way, the thing is, we want all
> of them to connect :-).
>
> Good luck,
>
> Dimiter
>
> --------------------------------------------------------------------
> Dimiter Popoff
> Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria
> http://transgalactic.freeyellow.com
>
>
>
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